ISO/TS 11819-3:2021 specifies two tyres intended to serve as reference tyres when using the close-proximity (CPX) method specified in ISO 11819-2.

The CPX method is a method for evaluating different road surfaces with respect to their influence on traffic noise, under conditions when tyre/road noise dominates. This method ideally requires the use of standardized tyres, which have noise characteristics that are broadly representative of the effect of road surfaces on the noise emission of passenger car and heavy vehicle tyres. However, such tyres are not specified in ISO 11819-2. This document serves to specify these standardized tyres.